It is one of the most hotly debated environmental topics of the year - whether the drive to produce alternative so-called green fuels will take food from the mouths of the hungry.

Is it ethical to burn food while people starve?

For environmental groups like Friends of the Earth, it's a no brainer.

"If you start to fuel cars with crops," says Ed Matthew, "you are instantly putting the world's one billion starving people in competition with the world's one billion motorists. It's as simple as that."

Green groups and aid agencies cite biofuels as forming part of the "perfect storm" of poor harvests, rising oil prices and a surge in demand for food from China and India that are all pushing up the price of everything from pasta to a loaf of bread.

In fact, the first flashpoint in the food versus fuel conflict has already happened.

Mexican anger at more expensive corn flour led to the so called "tortilla riots" at the beginning of the year.

The price rises were attributed to the United States' large-scale switch from food to fuel production, meaning less maize exported to its southern neighbour.

Misleading argument

However, a look at the bigger picture reveals that an apparent straight case of fuel taking precedence over food is misleading.

Biofuels could be in the vanguard of much higher standards for international trade in agricultural commodities

National Farmers Union's biofuels advisor Jonathan Scurlock

For years, Mexican dependency on cheap American corn had ruined the Mexican maize business and millions of farmers had left the land.

Now Mexicans are starting to grow maize again. It is a slow process, but it will start to reduce their dependency on the north.

And this is a key part of the debate, according to the UK National Farmers Union's biofuels advisor Jonathan Scurlock.

He thinks that greater demand for food and fuel could help galvanise agriculture in developing countries, which for many years have had their farming industries crushed by cheap imports.

Not just food

Farmers in the West point out that their past food surpluses dumped on developing world markets never alleviated hunger.

"This is all about 'trade not aid'," says Scurlock.

Car makers offer models powered by ethanol made from plants

"It would be a very good thing if developing countries could produce something that we in the West were prepared to pay a fair price for."

However, Friends of the Earth is sceptical that farmers in developing countries will see much benefit from the growth in bio fuels.

Mr Matthew says large global corporations and landowners are more likely to be the winners, while the small farmer will lose out.

Mr Scurlock concedes that in the short term food prices could rise.

"But let's be frank," he says, "the public can afford to pay more for quality food and the impact will be to bring more land worldwide into production."

Mr Scurlock firmly believes there is enough land worldwide to grow both food and fuel comfortably.

He says we would never have had such a massive tobacco industry if we had wanted only to use land for growing food crops.

Urgent issue

Indeed, United Nations figures show there to be around 2 billion hectares (f5 billion acres) of degraded land globally that could be put into production - 25% in Africa, 25% in Asia, 25% in the Americas; the rest scattered around the world in places like Ukraine and Kazakhstan.

This is land that has either been used for agriculture then abandoned or has been mismanaged or contaminated.

The environmental group, WWF produced a report earlier this year, concluding that 18 million hectares of rainforest in Southeast Asia are currently lying idle after being cleared for timber production.

This land could, if responsibly managed, says WWF, be used for palm oil production.

And that is the crux of the matter - the need to ensure that biofuels are ethically produced.

The issue is urgent.

In the UK, fuel suppliers are having to adapt to the Renewable Transport Fuel Obligation - requiring 5% of all fuel sold by 2010 to come from renewable sources.

There is growing concern that sourcing must be included in the environmental criteria set by the European Union.

But Mr Scurlock remains optimistic that biofuels will lead to an upturn for farmers everywhere.

"Biofuels could be in the vanguard of much higher standards for international trade in agricultural commodities," he says.

Radio 4's Costing the Earth: Food versus Fuel is broadcast on Thursday 4 October at 2100BST, repeated Friday 5 October at 1500BST.